Such detectors comprise a scintillator consisting of a membrane intercepting the X-rays and containing a material producing photons when hit by these rays, together with a camera system comprising a detection part preceded by an appropriate lens, placed behind the scintillator. The camera and the scintillator are fixed on a mounting uniting them and furthermore comprising an enclosure forming a darkroom between the scintillator and the camera system. In many detectors, the system is composed of a plurality of cameras sharing the field of vision and whose measurements are compiled by an electronic system to reconstitute a global image bigger than any a single camera could take.
Designers have to overcome the problem of maintaining a constant focal distance between the scintillator and the cameras, to avoid the risk of producing a blurred image. The causes of deformation are even more acute with large dimension detectors comprising a plurality of cameras. Measures have to be taken not only against mounting imprecision but also against deformations of the frame, of thermal or mechanical origin, resulting from the weight of the elements and the high temperatures they often have to withstand. In practice, prior art detectors do not provide sufficient guarantees of reliability. Thus, a detector comprises a frame in the form of a square box enclosing the darkroom. The scintillator is on the top face of the box, and the cameras are fixed to the four lateral faces. This mounting is very sensitive to deformations of the frame.